The effectiveness of online ads is generally measured on click-through rates, though with advanced ad tracking, you may also be able to measure ads by leads and sales. The standard for online ads has long been Google AdWords. Hubspot has identified three elements are crucial for high click-through rates on AdWords.

High Relevance - an effective ad is one that is 100% relevant for the search query, from the ad to the landing page

Compelling Call-to-Action - an ad should generate a sense of urgency in the user to click it now

Value Proposition - value can be lower prices, free shipping, an easy return policy, or a time limit for a sale

These elements are also important for Facebook ads. The big challenge on Facebook is to grab the attention of the user. Google users are actively searching for something. Facebook users are just checking in on their social lives. So Facebook ads must also have an element of distraction.

West ElmThis ad was seen by a college student, so it was well targeted. Words like ".edu" and "college" call attention to it, and the value is clearly stated.

Bud LightThis ad showed up for a man in his 30s. Obvious overlapping interests for Bud Light and the NFL. "Exclusively" means that this ads was created for Facebook fans only. The image attracts users with the promise of a video.

SamsungThe targeting isn't necessarily tight, but the value proposition is very clear. The image draws the eye with bright colors, the four phones featured and the $300.